Methods for improving high frequency reconstruction

• US 9,431,020 B2
• Filed: 04/18/2013
• Issued: 08/30/2016
• Est. Priority Date: 11/29/2001
• Status: Expired due to Term

• Current Assignee: Dolby International AB (Dolby Laboratories Incorporated)
• Original Assignee: Dolby International AB (Dolby Laboratories Incorporated)
• Inventors: Kjoerling, Kristofer, Ekstrand, Per, Hoerich, Holger
• Primary Examiner(s): Serrou, Abdelali
• Application Number:
  US13/865,450
• Publication Number:
  US 20130226597A1
• Time in Patent Office: 1,230 Days
• Field of Search: 704/205, 704501-503, 704/E21.011, 704/220, 704/E19.001, 704/E19.019
• US Class Current: 1/1
• CPC Class Codes: G10L 19/0017 Lossless audio signal coding; Perfect reconstruction of coded audio signal by transmission of coding error G10L19/24 takes precedence
• CPC Class Codes: G10L 19/0204 using subband decomposition
• CPC Class Codes: G10L 19/0208 Subband vocoders
• CPC Class Codes: G10L 19/028 Noise substitution, i.e. substituting non-tonal spectral components by noisy source comfort noise for discontinuous speech transmission G10L19/012
• CPC Class Codes: G10L 19/06 Determination or coding of the spectral characteristics, e.g. of the short-term prediction coefficients
• CPC Class Codes: G10L 19/07 Line spectrum pair [LSP] vocoders
• CPC Class Codes: G10L 19/093 using sinusoidal excitation models
• CPC Class Codes: G10L 19/167 Audio streaming, i.e. formatting and decoding of an encoded audio signal representation into a data stream for transmission or storage purposes
• CPC Class Codes: G10L 19/24 Variable rate codecs, e.g. for generating different qualities using a scalable representation such as hierarchical encoding or layered encoding
• CPC Class Codes: G10L 19/26 Pre-filtering or post-filtering
• CPC Class Codes: G10L 19/265 Pre-filtering, e.g. high frequency emphasis prior to encoding
• CPC Class Codes: G10L 21/038 using band spreading techniques

Abstract

The present invention proposes a new method and a new apparatus for enhancement of audio source coding systems utilizing high frequency reconstruction (HFR). It utilizes a detection mechanism on the encoder side to assess what parts of the spectrum will not be correctly reproduced by the HFR method in the decoder. Information on this is efficiently coded and sent to the decoder, where it is combined with the output of the HFR unit.

Claims

1. Audio decoder for decoding an encoded original audio signal, the encoded original audio signal comprising a lowband signal and one or more coded spectral lines, comprising:

a line decoder configured to decode the one or more coded spectral lines;

a decoder for decoding the encoded original audio signal to produce the lowband signal;

a high frequency reconstruction processor configured to perform a high frequency reconstruction processing by extrapolating the lowband signal to obtain a highband signal, wherein the decoded one or more spectral lines correspond to one or more differences between the original audio signal and the highband signal; and

a combiner configured to combine the decoded one or more spectral lines, the highband signal, and the lowband signal to obtain a decoded audio signal;

wherein one or more of the line decoder, the high frequency reconstruction processor, and the combiner are implemented, at least in part, by one or more hardware elements of the audio decoder.

2. The audio decoder of claim 1, wherein the line decoder comprises a parametric decoding of the one or more coded spectral lines or a waveform decoding of the one or more coded spectral lines.

3. The audio decoder of claim 1, further comprising a subband filter bank for synthesizing the decoded one or more spectral lines.

4. The audio decoder of claim 3, further comprising a core decoder for generating a decoded core audio signal, and wherein the subband filterbank is configured for synthesising the decoded one or more spectral lines together with the decoded core audio signal.

5. Method of audio decoding an encoded original audio signal, the encoded original audio signal comprising a lowband signal and one or more coded spectral lines, comprising:

decoding, by a line decoder, the one or more coded spectral lines;

decoding, by a decoder, the encoded original audio signal to produce the lowband signal;

performing, by a high-frequency reconstruction processor, a high frequency reconstruction processing by extrapolating the lowband signal to obtain a highband signal, wherein the decoded one or more spectral lines correspond to one or more differences between the original audio signal and the highband signal; and

combining, by a combiner, the decoded one or more spectral lines, the highband signal, and the lowband signal to obtain a decoded audio signal;

wherein one or more of the line decoder, the high frequency reconstruction processor, and the combiner are implemented, at least in part, by one or more hardware elements of the audio decoder.

6. Non-transitory storage medium having stored thereon a computer program for performing, when running on a computer or processor, a method of audio decoding an encoded original audio signal, the encoded original audio signal comprising a lowband signal and one or more coded spectral lines, the method comprising:

decoding, by a line decoder, the one or more coded spectral lines;

decoding, by a decoder, the encoded original audio signal to produce the lowband signal;

performing, by a high-frequency reconstruction processor, a high frequency reconstruction processing by extrapolating the lowband signal to obtain a highband signal, wherein the decoded one or more spectral lines correspond to one or more differences between the original audio signal and the highband signal; and

combining, by a combiner, the decoded one or more spectral lines, the highband signal, and the lowband signal to obtain a decoded audio signal.